LACK OF DIRECTED V-ALPHA-14-J-ALPHA-281 REARRANGEMENTS IN NK1(-CELLS() T)

NK1.1(+) T cells are an unusual subset of TCR alpha beta cells disting uished by their highly restricted V beta repertoire and predominant us age of an invariant V alpha 14-J alpha 281 chain. To assess whether a directed rearrangement mechanism could be responsible for this invaria nt alpha chain, we have analyzed V alpha 14 rearrangements by polymera se chain reaction and Southern blot in a panel of cloned T-T hybrids d erived from thymic NK1.1(+) T cells. As expected a high proportion (17 /20) of the hybrids had rearranged V alpha 14 to J alpha 281. However, V alpha 14-J alpha 281 rearrangements always occurred on only one chr omosome and were accompanied by other V alpha-J alpha rearrangements ( not involving V alpha 14) on the homologous chromosome. These data arg ue that rigorous ligand selection rather than directed rearrangement i s responsible for the high frequency of V alpha 14-J alpha 281 rearran gements in NK1.1(+) T cells.